Solids materials are often transported in mixture with liquids, either because the mixture in-and-of itself is desired, or because the addition of liquids to solids aids in the handling of the solids. For example, it is often easier to unload material from a tank when the material is in flowable form. Such mixtures or slurries can include for example, hazardous waste, non-hazardous waste, raw solids material, processed solids, beads, pellets, particles, grains, or chemical compounds contained in at least partial suspension with a diluent. In some instances the suspension may be substantially homogeneous, and in others it may be non-homogenous. The solids can be any pulverized, particulate, or other solids material which when mixed with a diluent, may become at least partially flowable. Examples of diluents include solvents, water, naphtha, paint thinner, bitumen, and other petroleum based materials; condensate, or any other liquid or material sufficient to render a mixture flowable.
When transporting mixtures over long distances, via road, rail, sea, or air, extended transportation time may facilitate a settling of solids on a bottom portion of a tank. When transportation time extends over many hours, days or even weeks, the challenge may increase significantly. For example, solids may settle in the liquids and gradually form a sediment on the bottom of a storage container e.g., tank, during storage and/or transport. As loads shift, the solids sediment may have varying thickness on the floor of the tank. As a slurry or other mixture is unloaded from the tank, the liquids portion of the mixture may be readily removed while a portion of the solids sediment may remain in the tank.
Depending on the particular circumstance, the retention of solids in the bottom of the tank may pose a number of challenges. Added cost may be required to remove retained solids, or otherwise, the tank's capacity may be diminished. In addition, if uniformity is desired at the time of tank unloading, a sedimentary tank may result in uniformity variances at the time of unloading. Depending on the circumstance, concentration differences or non-homogeneity may be undesirable at a receiving facility, and may result in rejection of the shipment of waste materials.
Raw material, virgin materials, and materials to be used in industrial processes may be transported without a portion of the liquid (e.g., water or solvents) in order to save weight and/or increase capacity. Adding liquids to the top of a load prior to offloading to reconstitute the materials into a mixture may also prove challenging.
In order to address these issues, tanks have been designed to include an agitator system to stir the mixture so that the slurry may be in a homogenous state when discharged from the tank. With some of these systems, the agitator may become embedded in solids material and may have difficulty mixing waste.